relibc n32 bring-up spike

Status: gate passed (research). 2026-10-25.

Upstream relibc is not n32-ready, but a contained port has been demonstrated. A patched relibc built a static, big-endian, n32 libc.a, and four smoke tests ran under qemu-mipsn32:

The raw result included:

hello: argc=1 tls=1234
setjmp: r=9 jumped=1 tls=5678
main: tls=100
thread: tls=42
joined: ret=43 main_tls=100

What it proves

The expensive unknowns for forking relibc are resolved: n32 big-endian codegen, static linking, TLS layout (TLS_DTV_AT_TP, TLS_TCB_OFFSET 0x7000), MIPS pthread clone argument order, the n32 syscall table, setjmp, and per-thread TLS. The port is about 224 changed lines plus a generated syscall backend; an IRIX PAL would need the same architecture seam.

What it does not prove

• Static linking only; no dynamic MIPS relocations or ld.so path.
• Signal/ucontext types are placeholders; delivery and sigreturn are untested.
• long double varargs and %Lf are approximate/untested.
• 64-bit syscall arguments are truncated by usize casts.
• The headers are not a full sysroot.
• The n32 syscall backend used for the QEMU gate is Linux, not the IRIX 7 native ABI. The provisional irix7-pal scaffold replaces it but has not been booted.
• Nightly-only, custom target, and QEMU-specific clone validation.

IRIX PAL scaffold (2026-10-25)

A provisional irix7-pal branch in the fork replaces the Linux sc backend with an irix7 module. It builds librelibc.a for the native target and links a C hello and an fs probe with no undefined symbols and no FP instructions.

This is not a working PAL. Neither binary has been executed on IRIX 7: the host has no system-mode MIPS emulator, and the probe cannot be meaningfully run under user-mode QEMU because IRIX syscall 15 (getpid) collides with Linux n32 mknod. The scaffold also guesses errno because the kernel has no error channel, has no TLS/thread pointer (MIPS III has no rdhwr), does not pass an auxiliary vector, and has a private 128-byte stat layout that differs from relibc’s 136-byte n32 layout. Signals, sockets, processes, lseek and the remaining POSIX surface are still ENOSYS walls.

The branch is at https://github.com/irix7/relibc/tree/irix7-pal. The next gate is a bootable probe on iris with a real negative-errno channel and a shared stat/directory ABI, not a success claim from linking alone.

Repository artefacts

The patched source, patch set, pristine sc 0.2.7 source, test sources and full report live in the dedicated repository:

https://github.com/irix7/relibc (branch irix7-n32); the PAL scaffold is on irix7-pal. Neither is wired into the kernel or release build.

Next

1. Harden the IRIX PAL scaffold: negative-errno channel, TLS/thread pointer, auxiliary vector and a shared stat/directory ABI.
2. Boot the linked fs probe on iris and only then replace the Linux sc gate.
3. Add the target spec and relibc patch queue to the forked relibc.
4. Add a mips64 crt0 to relibc proper.
5. Keep the IRIX std shim as the bring-up path until the relibc link succeeds.